Experiments and Observations on Different Kinds of Air Part 14

_Green copperas_ turned to a deeper green upon being put into acid air, which it absorbed slowly. _White copperas_ absorbed this air very fast, and was dissolved in it.

_Sal ammoniac_, being the union of spirit of salt with volatile alkali, was no more affected with the acid air than, as I have observed before, common salt was.

I also introduced to the acid air various other substances, without any particular expectation; and it may be worth while to give an account of the results, that the reader may draw from them such conclusions as he shall think reasonable.

_Borax_ absorbed acid air about as fast as blue vitriol, but without any thing else that was observable.

Fine white _sugar_ absorbed this air slowly, was thoroughly penetrated with it, became of a deep brown colour, and acquired a smell that was peculiarly pungent.

A piece of _quick lime_ being put to about twelve or fourteen ounce measures of acid air, and continuing in that situation about two days, there remained one ounce measure of air that was not absorbed by water, and it was very strongly inflammable, as much so as a mixture of half inflammable and half common air. Very particular care was taken that no common air mixed with the acid air in this process. At another time, from about half the quant.i.ty of acid air above mentioned, with much less quick-lime, and in the s.p.a.ce of one day, I got half an ounce measure of air that was inflammable in a slight degree only. This experiment proves that some part of the phlogiston which escapes from the fuel, in contact with which the lime is burned, adheres to it. But I am very far from thinking that the causticity of quick-lime is at all owing to this circ.u.mstance.

I have made a few more experiments on the mixture of acid air with _other kinds of air_, and think that it may be worth while to mention them, though nothing of consequence, at least nothing but negative conclusions, can be drawn from them.

A quant.i.ty of common air saturated with nitrous air was put to a quant.i.ty of acid air, and they continued together all night, without any sensible effect. The quant.i.ty of both remained the same, and water being admitted to them, it absorbed all the acid air, and left the other just as before.

A mixture of two thirds of air diminished by iron filings and brimstone, and one third acid air, were mixed together, and left to stand four weeks in quicksilver. But when the mixture was examined, water presently imbibed all the acid air, and the diminished air was found to be just the same that it was before. I had imagined that the acid air might have united with the phlogiston with which the diminished air was overcharged, so as to render it wholsome; and I had read an account of the stench arising from putrid bodies being corrected by acid fumes.

The remaining experiments, in which the acid air was princ.i.p.ally concerned, are of a miscellaneous nature.

I put a piece of dry _ice_ to a quant.i.ty of acid air (as was observed in the section concerning _alkaline_ air) taking it with a forceps, which, as well as the air itself, and the quicksilver by which it had been confined; had been exposed to the open air for an hour, in a pretty strong frost. The moment it touched the air it was dissolved as fast as it would have been by being thrown into a hot fire, and the air was presently imbibed. Putting fresh pieces of ice to that which was dissolved before, they were also dissolved immediately, and the water thus procured did not freeze again, though it was exposed a whole night, in a very intense frost.

Flies and spiders die in acid air, but not so quickly as in nitrous air.

This surprized me very much; as I had imagined that nothing could be more speedily fatal to all animal life than this pure acid vapour.

As inflammable air, I have observed, fires at one explosion in the vapour of smoking spirit of nitre, just like an equal mixture of inflammable and common air, I thought it was possible that the fume which naturally rises from common spirit of salt might have the same effect, but it had not. For this purpose I treated the spirit of salt, as I had before done the smoking spirit of nitre; first filling a phial with it, then inverting it in a vessel containing a quant.i.ty of the same acid; and having thrown the inflammable air into it, and thereby driven out all the acid, turning it with its mouth upwards, and immediately applying a candle to it.

Acid air not being so manageable as most of the other kinds of air, I had recourse to the following peculiar method, in order to ascertain its _specific gravity_. Having filled an eight ounce phial with this air, and corked it up, I weighed it very accurately; and then, taking out the cork, I blew very strongly into it with a pair of bellows, that the common air might take place of the acid; and after this I weighed it again, together with the cork, but I could not perceive the least difference in the weight. I conclude, however, from this experiment, that the acid air is heavier than the common air, because the mouth of the phial and the inside of it were evidently moistened by the water which the acid vapour had attracted from the air, which moisture must have added to the weight of the phial.

SECTION V.

_Of INFLAMMABLE AIR._

It will have appeared from my former experiments, that inflammable air consists chiefly, if not wholly, of the union of an acid vapour with phlogiston; that as much of the phlogiston as contributes to make air inflammable is imbibed by the water in which it is agitated; that in this process it soon becomes fit for respiration, and by the continuance of it comes at length to extinguish flame. These observations, and others which I have made upon this kind of air, have been confirmed by my later experiments, especially those in which I have connected _electrical experiments_ with those on air.

The electric spark taken in any kind of _oil_ produces inflammable air, as I was led to observe in the following manner. Having found, as will be mentioned hereafter, that ether doubles the quant.i.ty of any kind of air to which it is admitted; and being at that time engaged in a course of experiments to ascertain the effect of the electric matter on all the different kinds of air, I had the curiosity to try what it would do with _common air_, thus increased by means of ether. The very first spark, I observed, increased the quant.i.ty of this air very considerably, so that I had very soon six or eight times as much as I began with; and whereas water imbibes all the ether that is put to any kind of air, and leaves it without any visible change, with respect to quant.i.ty or quality, this air, on the contrary, was not imbibed by water. It was also very little diminished by the mixture of nitrous air. From whence it was evident, that it had received an addition of some other kind of air, of which it now princ.i.p.ally consisted.

In order to determine whether this effect was produced by the _wire_, or the _cement_ by which the air was confined (as I thought it possible that phlogiston might be discharged from them) I made the experiment in a gla.s.s syphon, fig. 19, and by that means I contrived to make the electric spark pa.s.s from quicksilver through the air on which I made the experiment, and the effect was the same as before. At one time there happened to be a bubble of common air, without any ether, in one part of the syphon, and another bubble with ether in another part of it; and it was very amusing to observe how the same electric sparks diminished the former of these bubbles, and increased the latter.

It being evident that the _ether_ occasioned the difference that was observable in these two cases, I next proceeded to take the electric spark in a quant.i.ty of ether only, without any air whatever; and observed that every spark produced a small bubble; and though, while the sparks were taken in the ether itself, the generation of air was slow, yet when so much air was collected, that the sparks were obliged to pa.s.s through it, in order, to come to the ether and the quicksilver on which it rested, the increase was exceedingly rapid; so that, making the experiment in small tubes, as fig. 16, the quicksilver soon receded beyond the striking distance. This air, by pa.s.sing through water, was diminished to about one third, and was inflammable.

One quant.i.ty of air produced in this manner from ether I suffered to stand two days in water, and after that I transferred it several times through the water, from one vessel to another, and still found that it was very strongly inflammable; so that I have no doubt of its being genuine inflammable air, like that which is produced from metals by acids, or by any other chemical process.

Air produced from ether, mixed both with common and nitrous air, was likewise inflammable; but in the case of the nitrous air, the original quant.i.ty bore a very small proportion to the quant.i.ty generated.

Concluding that the inflammable matter in this air came from the ether, as being of the cla.s.s of _oils_, I tried other kinds of oil, as _oil of olives_, _oil of turpentine_, and _essential oil of mint_, taking the electric spark in them, without any air to begin with, and found that inflammable air was produced in this manner from them all. The generation of air from oil of turpentine was the quickest, and from the oil of olives the slowest in these three cases.

By the same process I got inflammable air from _spirit of wine_, and about as copiously as from the essential oil of mint. This air continued in water a whole night, and when it was transferred into another vessel was strongly inflammable.

In all these cases the inflammable matter might be supposed to arise from the inflammable substances on which the experiments were made. But finding that, by the same process I could get inflammable air from the _volatile spirit of sal ammoniac_, I conclude that the phlogiston was in part supplied by the electric matter itself. For though, as I have observed before, the alkaline air which is expelled from the spirit of sal ammoniac be inflammable, it is so in a very slight degree, and can only be perceived to be so when there is a considerable quant.i.ty of it.

Endeavouring to procure air from a caustic alkaline liquor, accurately made for me by Mr. Lane, and also from spirit of salt, I found that the electric spark could not be made visible in either of them; so that they must be much more perfect conductors of electricity than water, or other fluid substances. This experiment well deserves to be prosecuted.

I observed before that inflammable air, by standing long in water, and especially by agitation in water, loses its inflammability; and that in the latter case, after pa.s.sing through a state in which it makes some approach to common air (just admitting a candle to burn in it) it comes to extinguish a candle. I have since made another observation of this kind, which well deserves to be recited. It relates to the inflammable air generated from oak the 27th of July 1771, of which I have made mention before.

This air I have observed to have been but weakly inflammable some months after it was generated, and to have been converted into pretty good or wholesome air by no great degree of agitation in water; but on the 27th of March 1773, I found the remainder of it to be exceedingly good air. A candle burned in it perfectly well, and it was diminished by nitrous air almost as much as common air.

I shall conclude this section with a few miscellaneous observations of no great importance.

Inflammable air is not changed by being made to pa.s.s many times through a red-hot iron tube. It is also no more diminished or changed by the fumes of liver of sulphur, or by the electric spark, than I have before observed it to have been by a mixture of iron filings and brimstone.

When the electric spark was taken in it, it was confined by a quant.i.ty of water tinged blue with the juice of archil, but the colour remained unchanged.

I put two _wasps_ into inflammable air, and let them remain there a considerable time, one of them near an hour. They presently ceased to move, and seemed to be quite dead for about half an hour after they were taken into the open air; but then they came to life again, and presently after seemed to be as well as ever they had been.

SECTION VI.

_Of FIXED AIR._

The additions I have made to my observations on _fixed air_ are neither numerous nor considerable.

The most important of them is a confirmation of my conjecture, that fixed air is capable of forming an union with phlogiston, and thereby becoming a kind of air that is not miscible with water. I had produced this effect before by means of iron filings and brimstone, fermenting in this kind of air; but I have since had a much more decisive and elegant proof of it by _electricity_. For after taking a small electric explosion, for about an hour, in the s.p.a.ce of an inch of fixed air, confined in a gla.s.s tube one tenth of an inch in diameter, fig. 16, I found that when water was admitted to it, only one fourth of the air was imbibed. Probably the whole of it would have been rendered immiscible in water, if the electrical operation had been continued a sufficient time.

This air continued several days in water, and was even agitated in water without any farther diminution. It was not, however, common air, for it was not diminished by nitrous air.

By means of iron filings and brimstone I have, since my former experiments, procured a considerable quant.i.ty of this kind of air in a method something different from that which I used before. For having placed a pot of this mixture under a receiver, and exhausted it with a pump of Mr. Smeaton's construction, I filled it with fixed air, and then left it plunged under water; so that no common air could have access to it. In this manner, and in about a week, there was, as near as I can recollect, one sixth, or at least one eighth of the whole converted into a permanent air, not imbibed by water.

From this experiment I expected that the same effect would have been produced on fixed air by the fumes of _liver of sulphur_; but I was disappointed in that expectation, which surprised me not a little; though this corresponds in some measure, to the effect of phlogiston exhaled from this substance on acid air. Perhaps more time may be requisite for this purpose, for this process was not continued more than a day and a night.

Iron filings and brimstone, I have observed, ferment with great heat in nitrous air, and I have since observed that this process is attended with greater heat in fixed air than in common air.

Though fixed air incorporated with water dissolves iron, fixed air without water has no such power, as I observed before. I imagined that, if it could have dissolved iron, the phlogiston would have united with the air, and have made it immiscible with water, as in the former instances; but after being confined in a phial full of nails from the 15th of December to the 4th of October following, neither the iron nor the air appeared to have been affected by their mutual contact.

Having exposed equal quant.i.ties of common and fixed air, in equal and similar cylindrical gla.s.s vessels, to equal degrees of heat, by placing them before a fire, and frequently changing their situations, I observed that they were expanded exactly alike, and when removed from the fire they both recovered their former dimensions.

Having had some small suspicion that liver of sulphur, besides emitting phlogiston, might also yield some fixed air (which is known to be contained in the salt of tartar from which it is made) I mixed the two ingredients, viz. salt of tartar and brimstone, and putting them into a thin phial, and applying the flame of a candle to it, so as to form the liver of sulphur, I received the air that came from it in this process in a vessel of quicksilver. In this manner I procured a very considerable quant.i.ty of fixed air, so that I judged it was all discharged from the tartar. But though it is possible that a small quant.i.ty of it may remain in liver of sulphur, when it is made in the most perfect manner, it is not probable that it can be expelled without heat.

SECTION VII.

MISCELLANEOUS EXPERIMENTS.